1. Field of the Invention
The invention relates to a hydrogen extraction (/separation) unit for extracting hydrogen from a hydrogen-containing gas that contains hydrogen
2. Description of the Related Art
As a unit for extracting hydrogen from a hydrogen-containing gas, there has been known a unit making use of a hydrogen separation film including a metal that selectively allows penetration of hydrogen (e.g., palladium or a palladium alloy). Such a hydrogen extraction unit is employed, for example, in a fuel cell system having a fuel cell.
A fuel cell is designed to be supplied with fuel gas containing hydrogen and to obtain an electromotive force by an electrochemical reaction. As a method of applying a hydrogen extraction unit to a fuel cell system, it has been known to extract hydrogen from reformed gas (hydrogen-rich gas) obtained by reforming a hydrocarbonic fuel by means of the hydrogen extraction unit and to supply a fuel cell with the hydrogen thus obtained. In the hydrogen extraction unit thus constructed, if a flow channel through which the aforementioned reformed gas flows is formed on the side of one face of a hydrogen separation film, only the hydrogen contained in the reformed gas penetrates the hydrogen separation film. Hence, the hydrogen can be extracted in a flow channel formed on the side of the other face of the hydrogen separation film.
There has been proposed a hydrogen extraction unit equipped with a hydrogen separation film, which is constructed by laminating a plurality of first members, hydrogen separation films, and second members (see Japanese Patent Application Laid-Open No. 6-345408 and the like). Each of the first members constitutes a flow channel layer through which a hydrogen-containing gas such as the aforementioned reformed gas flows. Each of the second members constitutes a flow channel layer through which hydrogen extracted by the hydrogen separation film flows. By thus laminating the two members constituting the flow channel members between which the hydrogen separation film is interposed, it becomes possible to ensure a wider surface area of the hydrogen separation film in the unit as a whole and to enhance the hydrogen extraction efficiency.
However, not much consideration has been given so far to a method of connecting the flow channel constituting members and the hydrogen separation film when laminating them as described above. A structure for connecting flow channels constituted through lamination of members or a structure for ensuring airtightness of flow channels is required in end portions of each of the members that have been laminated.
As in the case where the hydrogen extraction unit thus constructed is installed in a vehicle together with a fuel cell and where the fuel cell is used as a power source for driving the vehicle, if the hydrogen extraction unit is used for purposes with a restricted space for installation, further reduction in size is desired. For example, as a construction for connecting a plurality of members with ensured airtightness, it has been known to dispose sealing members such as gaskets among the members to be connected. Nevertheless, such a concrete construction of the hydrogen extraction unit as will permit further reduction in size has been desired.
The invention has been made to solve the aforementioned problems of the related art. It is thus an object of the invention to provide an art for connecting members constituting a hydrogen extraction unit in such a manner as to permit further reduction in size of the hydrogen extraction unit.
To achieve the object stated above, the invention provides a hydrogen extraction unit which is designed to extract hydrogen from a hydrogen-containing gas that contains hydrogen and which comprises a hydrogen separation member, a first flow channel member, and a second flow channel member. The hydrogen separation member is designed as a thin metal plate member equipped with a hydrogen separation film that selectively allows penetration of hydrogen. The first flow channel member is disposed in a laminated manner, is designed as a thin metal plate member, is disposed adjacent to a first face of the hydrogen separation member, is bonded to the hydrogen separation member by a bonding method free from fusion of a base material, and constitutes, together with the hydrogen separation member adjacent to the first flow channel member, a hydrogen-containing gas flow channel and through which the hydrogen-containing gas flows. The second flow channel member is disposed in a laminated manner, is designed as a thin metal plate member, is disposed adjacent to a second face of the hydrogen separation member, is bonded to the hydrogen separation member by a bonding method free from fusion of a base material, and constitutes, together with the hydrogen separation member adjacent to the second flow channel member, a hydrogen flow channel and through which hydrogen penetrating the hydrogen separation film and extracted from the hydrogen-containing gas flows.
The invention also relates to a method of manufacturing a hydrogen extraction unit for extracting hydrogen from a hydrogen-containing gas that contains hydrogen. This method comprises the steps of preparing a hydrogen separation member designed as a thin metal plate member equipped with a hydrogen separation film that selectively allows penetration of hydrogen, preparing a flow channel member designed as a thin metal plate member and equipped with a flow channel constituting portion for constituting a gas flow channel between itself and the hydrogen separation member that is adjacent to the flow channel member when the hydrogen extraction unit has been assembled, laminating a plurality of members including the hydrogen separation member and the flow channel member in a predetermined sequence, and bonding the hydrogen separation member and the flow channel member together by a bonding method free from fusion of a base material.